Refrigerating system using dry ice and including a secondary heat exchange circuit



Oct. 5, 1948. R. BRuNslNG REFRIGERATING SYSTEM USING DRY ICE ANDINCLUDIN .A SECONDARY HEAT EXCHANGE CIRCUIT 2 Sheets-Sheet 1 Filed July13, 1946 INVENTOR. Rli l.. Bmmnngs Oct. 5, 1948. R. BRUNSING 2,450,713

REFRIGERTING SYSTEM USING DRY ICE AND, INCLUDING A SECONDARY HEATEXCHANGE CIRCUIT FiledJuly 1:5, 194s z slmtpsrmt 2 INVEN TOR. Ru L.Bnvuome Patented Oct. 5, 1948 REFRIGERATING SYSTEM USING DRY 4ICE ANDINCLUDING A SECONDARY HEAT EX- CHANGE CIRCUIT Rex L. Brunsing, SanFrancisco, Calif. n Application July 13, 1946, Serial No. 683,511

12 Claims.

This invention relates to a refrigerating system, and more particularlyto an improved apparatus and method for utilizing solid carbon dioxide(CO2), commonly called dry ice, or lvery cold materials of that generalcharacter having the property of changing from a solid state directlyinto a gaseous state.3 and absorbing heat during the change.

One of the objects of this invention is the provision of a system thatis more ecient than heretofore and which system employs a fluid orliquidrefrigerant that is chilled or cooled by being brought into heattransfer relationship with the dry ice and that is then conducted tothe'space or region to be refrigerated for cooling Suchregion, and thatis then returned to the dry ice for re-cooling and for repeating thecycle.

Another object of the invention is a refrigerating system that employsdry ice for cooling the refrigerant to be circulated in the region to becooled, and which system uses a more emcient and reliable means foreffecting such circulation than heretofore.

For the most part, prior systems of the general type to which thisinvention relates, have included a liquid refrigerant or fluid of verylow freezing point, which fluid has been chilled by dry ice and thencarried to cooling coilsor units in the region to be refrigerated afterwhich the fluid has been returned for re-cooling or chilling and for re'circulation. This circulation has been effected by the use of gaspressure developed in the container for the dry ice used for cooling thefluid, or else the circulation has been effected mechanically, andthermostatic controls have been used to regulate the flow of the uid.

Among the disadvantages of the system that employs the gas pressure forcirculating the Vfluid has been the fact that the procedure ofreplenishing the supply of dry ice in the large containers 4 resulted inloss of the gas pressure, and also at any time the large tank might'bevented to the atmosphere (which has beenthe common practice in using thegas for moving the fluid), the gas pressure is lost or radicallyreduced, and must be built up again before the system is operative.

Another objection is the fact that dry ice under gas pressure has lesscooling efficiency than where it is under atmospheric pressure. Dry icein sublirning under atmospheric pressure produces a temperature of-108.8 F. while under even a five pound pressure it will produce atemperature of only about -90 F. or about 18 degrees higher than werethe same at atmospheric pressure.

A still further disadvantage in using the gas pressure from the primecooling agent (solid CO2) is the fact that the large tanks used must bemade to withstand far greater pressures than are (Cl. .6ft-91.5)

, 2 normally used, with the result that they are very heavy andexpensive.

There areother disadvantagea'but the above are perhaps among theprincipal ones. 5 With the present invention 'the above objections areentirely overcome. lThe full cooling eillciency of the dry ice atatmospheric pressure is obtained. No large, expensive, and heavypressure tanks are required, and there is no wasteful venting of gaspressure nor is therel an objectionably'long delay between reductions inthe gas pressurev and the re-building of such pressure to the workingpoint.

Other objects and advantages will appear in the description and in thedrawings.

In the drawings, Fig; 1 is a diagrammatic plan view of a systemembodying thepresent invention as applied to a refrigerator car, theoutline of the Awalls of the latter, including the wall between the icebunker and the mainbody of the car being indicated in dot-dash lines. f

at right angles to the point of view of Fig. 4."

Fig. 6 is an enlarged sectional view through the upper part of thecontrol chamber taken along line 6--6 of Fig. 5.

Fig. 7 is a diagrammatic view clearly showing the system and manner ofoperation. e

Fig. 8 is a diagrammatic viewacross a car.

Fig. 9 is an enlargedsectional view along line 9-9ofFig.1.

0 In detail, the system, in its broad aspect, comprises a support i forholding a quantity of dryl ice that functions solely for chilling orcooling the fluid refrigerant. The v latter may be alcohol, brine, orany other suitable fluid. The dry ice-on said support is underatmospheric pressure, and

in a standard refrigerator car the amount of dry ice so supported may beabout 6000 lbs.

` Adjacent the support I, but not necessarily a part-of the'same, isaclosed tank or container 2 for holding a relatively-small amount of dryice. Where 6000 lbs might be held on support I, only about 500 lbs.would be in container 2, assuming the system were used in a standardrefrigerator car. In any event, a relatively small amount of dry ice isin container! and the container is relatively small as best indicatedgenerally in Fig. 1. n

Alongside container 2 is a control chamber :3. This chamber 3 isconnected with a cooling unit oo or units 4 for receiving a uidrefrigerant from Fig. 2 is anv enlarged plan view of the supportl saidunit or units. Chamber 3 is in communication with the gas in container2, which gas results from sublimation oi the dry ice in container and isunder pressure. The gas. undervpressure, is utilized to force the fluidrefrigerant from the control chamber past the main body of CO2 throughsupport I, and to the cooling coils or units 4 and back to controlchamber 3. ,Cooling units 4 are in the space to be refrigerated, andthers'nostatic means l. which includes a valve, functions for openingorclosing the'i'luid line to ow of uid to the `control chamber.r

The support I, container12.- and control cham--` ber 3, may all bepositioned in a conventional ice bunker at one end oi a refrigeratorcar. VThe dry ice on-support I will sublime at atmospheric boss that isclosed at its upper end by a cap 2|, and 'that is formed with ahorizontal wall 22 spaced slightly below said cap. Spaced slightlybelowthe wall 22 is a relatively thick block 23 secured to said boss andhaving one or moreof its sides grooved to provide a passageway 24communicating between the spaces above and below said blockrespectively.

The block 23 and wall 22 are coaxially apertured for passing a verticalrod that extends to about the lower end of cylinder I9 and coaxiallywith the latter.

pressure producinga temperature as low as -108.0 F., while there ispreferably about a 5 lb. pressure in tank 2. Therefore. when suchpressure exists, a temperature o! only about 90 F.

will be produced by the dry ice in the tank 2.

However, the ice in tank 2 isnotused-for cooling the liquid refrigerant,although it tends to pre- Vcool said refrigerant as will later beexplained.

Taking up the elements more in detail, the support I; preferably isformed to provide a corrugated upper surface of adjoining tooth-likeridges of vinverted V-shape and formed by corrugating a pieceof sheetmetal of the desired size. This sheet is secured on a nat sheet wherebya plurality of elongated parallel passageways B of tri- A the uppercorrugated side of support VI has a considerablearea in heat exchangerelationship with the two upper sides of said passageway. Substantiallytwo thirds of the walls of each pas sageway are inyheat exchangerelationship with the dry ice and this can be `increased by increasingthe area of the upper sides Vof the support by making the apices ofthecorrugations sharper.

'I'he closed container `2 may be of any desired shape, such ascylindrical or square, but it is preferably oblong and extendsvertically for convenience in tting in the end portion of a car and togive as much capacity-as is possible for its size. This container may bein one end of the conventional ice bunker II (Fig. 1') in a refrigeratorcar adjacent one end of support I and it may be spaced from the supportI by a wall I2 (Fig. 2) if desired to protect the same from possibleinjury in loading dry ice onto support I, and a central baille orseparator plate I3 in the tank 2 and terminating short of the bottom ofthe latter may be provided 'to prevent objectionable shifting of the dryice in the'container during movement of the car. AA removable gas tightclo sure I3' on container 2 is provided to enable loading the containerwith dry ice.

The control chamber is preferably alongside the container 2 and securedto the latter. In fact, one of the side walls I4 ofcontainer 2 is also aside wall of controlchamber 3 (Figs. 4, 6). Control chamber 3 isseparated internally into an upper compartment I5 and a, lowercompartment I5 by a horizontalv partition I1 (Figs. 4, 5, 7).

A removable, gas tight closure plate I9 closes on opening in the top ofthe upper compartment, which plate carries a depending cylinder I9 thatis open at its lower end, and which lower end is spaced above partitionI1 (Figs. 5, 6).

Concentric with cylinder I9, the head or closure Il is formed with anlupstanding cylindrical The opening in wall 22 is relatively large an hasbeveled edges for seating a poppet type valve 25' secured on the upperend of rod 25 when said rod is moved downwardly, and which valve willmove away from the opening upon moving the rod 25 upwardly. l

The aperture 21 through the block 23 may be providedwith a bushing formaking a sliding t with rod 25, but the said aperture is counterbored atits lower end to form an enlarged recess 28 that opens downwardly, theedges of said recess are beveled to form a seat for a ksecond poppettype valve 29, also secured on rod 25, and which valve closes the recessupon upward movement, but opens it when rod 25 moves downwardly.

A passageway 30 communicates at one of its ends with recess 29 and atits opposite end with the atmosphere. Within the cylinder I9 is adrum-like float 3| having a central passageway 32 through which rod 25freely passes, and the periphery of said iioat is relatively close tothe inner sides of said cylinder whereby'the latter will function as aguide for the float as lthe latter moves vertically up or down, as willlater be explained.

A collar 35 is secured on rod 25 at a point adjacent to, but preferablyspaced below the valve 29, while a second collar 35 is secured on rod 25adjacent the lower end of the latter. The iioat 3l` moves between thesecollars as the liquid level in the uppercompartment I5 rises or falls.

VWhen the level of such liquid rises suiliciently,

the float will engage the collar 35 and move the valve 29 to closedposition closing off the passageway 30, and opening valve 26, and whenthe liquid level falls suiiiciently, the oat moves down until it strikesthe collar 35, causing the valve 29 to open and valve 26 to close.

The cooling units 4 are preferably several in number, according to thespace to be refrigerated, and in the case of a refrigerator car, theyare disposed along the two opposite sides of the car adjacent the roof(Figs. l, 8, 9).

Each of the units 4 comprises a pair of oblong fiat plates 4Iv (Fig. 9)that'are elongated in direction of the length of the car (Fig. l), andwhich plates are spaced apart by parallel strips 42 (Fig. 9) extendinglongitudinally of said plates thereby providing a passageway 43 betweeneach adjacent pair of strips. Headers 44, 45 are at opposite ends ofeach cooling unit and at diagonally opposite corners.

Where, as in Fig. 1, there are two cooling units along each of the twolongitudinally extending sides of the car, the said units are in end toend spaced relationship along each side and the adjacent headers 44, 45of each pair are joined by a pipe 41 while the corresponding headers 45at the end of the car opposite the bunker Il are connected by a pipe 48in which the thermostatic device' including the valve is interposed forcontrolling the flow of a liquid refrigerant through passageways 59 atthe sides of the car.

in the same -8, 9

said units. and to a pipe 48 that connects with the header 8 'of thesupport I. j

'I'he outline of the inside of the car, in plan view, is indicated at 56(Figure 1) in dot-dash line, and the partition dividing the bunker fromthe main space to be refrigerated is indicated at 5I. The sides of thecar are indicated at 52 in Fig. 9 while the roof or top is designated 53and the. floor 54. Floor racks 55 are spaced above iloor 54 by strlngers56 that are cross bored at 5'I for ventilation. A false side wall 58 maybe spaced from each. side wall 52 to provide air passageways 59 thatextend to points slightly below the cooling units. Deilectors 6 0 may bepositioned across'the upper open lends of passageways 59 at spacedpoints to deect some of the air into the space through the car,generally in the samemanner as the cooling units and drip pans aresuspended in United States Letters Patent to Brown, No.

2,287,492 of June 2'3, 1942.

The space between top 53 of the car and the cooling units, and thespaces between the cooling units and the baille plates 66 provide airpassageways for generally downward movement of air from inside lthe carto the upper open ends of the 'Ihe air thenmoves fro'm the lower ends ofsaid passageways 59 to below the flow racks and then through said racksto the top of the car for re-circulation path, as seen by the arrows inFigs.

Referring back to thecontrol chamber, the

i closure I8 and boss 20 are preferably drilled to provide a passageway65 for gas, which passageway opens at one end into the space between thewall 22 in boss 20 and the cap 2 I, the latter being threadedly securedon the boss. The opposite end of said passageway connects with a pipe 66that opens into the container 2.

A pipe 6'I opens at one end into container 2 and at its opposite endinto the upper end of the lower compartment I6 of the control chamber(Figs.

A pipe 68 connects at one end with the control units 4 that are nearestthe bunker I I` (Figs. 1, 7) and a pipe or passageway 69 connects header8 with the lower end of the lower compartment I 6.

A drain tube I extends from the partition I1 to the lower end of lowercompartment I6 and is provided with a check valve 'II at its lower end.A check valve 'I2 is also preferably in the line 69 (Fig. 7). A

In operation, the lower compartment I6 contains a supply 80 (Fig. 7) ofa liquid refrigerant and the cooling units and pipes 48, 49 also containthe refrigerant. Y

As long as the valve is open (which would indicate a sufticiently hightemperature in the storage' space that is to be refrigerated to requirecirculation of the refrigerant) the control chamber j will function toeiTect intermittent circulation of the refrigerant through the coolingcoils. The position of the parts in the control chamber as seen in Fig.'I is one in which acirculation of the refrigerant through the coolingunits is ready to occur, assuming valve 5 is open.

Asseen in Fig. 7, the gas pressure in container 2Yis on the liquid 88 inlower compartment I6 and will force the liquid refrigerant through pipe59, support I (where it will be cooled), 'and pipe 49 to the coolingunits. The liquid in said units will be caused to ilow into the u ppercompartment' I5 causing float 3| to rise until the iioat strikescollar`35 and lifts the valve rod 25 with valves 25, 29. The valve 26will open admitting gas under pressure into the upper compartment, andvalve 29 will close vent 38, whereby the pressures in the upper andlower compartments will be equalized thereby permitting the liquid inthe upper compartment to ow by gravity into the lower compartment. Theiloat'3l will then move downwardly as the liquid drains from the uppercompartment, until it strikes the lower collar 36 overcoming the backpressure exerted on valve 29, which pressure has held valve V29 on rod25 in place thereby closing 'valve 26 and opening valve 29. This willvent the gas in the upper compartment through the vent 30 and the cycleabove described will be repeated until valve 5 is closed. The provisionof the cylindrical guide I9 in the control chamber insures operation ofthe oat under .all conditions. The said guide is perforated at 8| topermit free drainage of the liquid refrigerant, but the walls of theguide member are imperforate for a substantial distance above theuppermost perforations with the result that a substantial quantity ofgas is trapped in the space 82 (Fig. 6) in the upper endk of the uppercompartment after the float 3| has lifted the valve rod, hence theopening of the valve 29 does not effect'a venting of all the gas in thecontrol chamber. 'I'here is an appreciable saving of gas by thisstructure, which is quite important.

The sublimation of the dry ice in the container 2 will produce atemperature as low as --90 F., when the said ice is under 5 lbs. pres- Asure, which is about the desired maximum pressure forv forcing therefrigerant through the circuit. However, the dry ice in support I willproduce a. temperature of practically -109`F., since it is underatmospheric pressure. A much greater. cooling is thereby obtained than.were the dry ice that is used for cooling also used yto produce the gaspressure.

The use of dry ice to produce the gas pressure is important for severalreasons. It is easily controlled Land its temperature is such as to notraise the temperature of the liquid refrigerant that passes through thecontrol chamber.

It is also apparent from the description that the main supply of dry icemay be replenished at any time without causingthe slightest delay in thefunctioning of the circulating system.

Furthermore, the smallness of the container 2 makes it relatively cheapand light in weight even if made to withstand a relatively highpressure, which is made imperative by many public carriers even though amuch lighter tank or container would be safe. A conventional safetyvvalve 'I5`that is adjustable for maximum pressure insures against anypossible danger from I facture, said container 2 may be separate from vthe control chamber and spaced any desired distance from it. The rate ofsublimation of the dry ice in the container 2 isadequate to main tain aworking pressure of gas in the control tive thereof.

Il claim:

1. In a refrigeration system, a support for holding a body of solid CO:in communication with the atmosphere for maintaining said body atsubstantially atmospheric pressure during sublimation thereof, avclosedcontainer for holding a substantially smaller amount of solid CO2 thansaid body and under the pressure of the C: gas resulting fromsublimation of saidv smaller amount, a'liquid refrigerant, a continuousconduit, including a cooling unit, enclosing said refrigerant formovement thereof in one direction in a closed path of travel, one of thewalls of said conduit being in direct heat transfer relationship withsaid body at a point in the length of said conduit for coolingsaidrefrigerant at said point, means comprising a body of said refrigerantin said conduit disposed in direct pressure contact with the CO: gasfrom said container for effecting said movement of said refrigerant insaid path under the influence of the pressure of said gas. 2. In arefrigeration system, a support for holding a body of solid CO: incommunication with the atmosphere for maintaining said body atsubstantially atmospheric pressure during sublimation thereof, a closedcontainer for holding a substantially smaller amount of solid CO: than isaid body under the pressure of the C0'.` gas resulting from sublimationof said smaller amount, a liquid refrigerant, a continuous conduit,including a cooling unit, enclosing said refrigerant for movementthereof in one direction in a closed path of travel, one of the walls ofsaid conduit being in direct heat transfer rela--v tionship with saidbody at a point in the length of said conduit for cooling saidrefrigerant at said point, means comprising a body of said refrigerantin said conduit disposed in direct pressure contact with the CO2 igasfrom said container for effecting said movement of said refrigerant insaid path under the influence of the pressure of said gas, saidcontainer, support and means being adjacent each other. f

i 3. In a refrigeration system, a support for holding a body of solidCO: in communication with the atmosphere for maintaining said body atsubstantially atmospheric pressure during sublimation thereof, a closedcontainer for holding a substantially smaller amount of solid CO2 thansaid body under the pressure of the CO: gas resulting from sublimationof said smaller amount, a liquid refrigerant, a continuous conduit,including a cooling unit, enclosing said refrigerant for movementthereof in one direction in a closed path of travel, one of the walls ofsaid conduit being in direct heat transfer relationship with said bodyat a point in the length of said conduit for cooling 'said refrigerant`at said point, means comprising a body of said refrigerant in saidconduit disposed in direct pressure contact with the `CO: gas from saidcontainer for effectingl said movement of said refrigerant in said pathunder the influence of the pressure of said gas, arefrigeratcr carhaving a compartment at one end thereof, said container, support andmeans being in said compartment and said cooling unit being in theremaining portion of said car adjacent the junctures between thesidewalls and roof of such car and extending the length of the latter. v

4; In a refrigeration system, a support for holding a body of solid CO:thereon in communication with the atmosphere for maintaining said bodyat substantially atmospheric pressure during sublimation thereof, aclosed container for hold-` ing a substantially smaller amount of solidCO: than said body under pressure of the CO: gas resulting fromsublimation of said smaller amount, a liquid refrigerant, a continuousconduit, including a cooling unit, enclosingsaid'refrigerant formovement thereof in one direction in' a closed path of travel, saidsupport comprising a portion of one of the walls of said conduit wherebysaid refrigerant will be cooled upon passing said support, anotherportion of said conduit being enlarged and alongside said container,means comprising a body of said refrigerant in said enlarged portiondisposed in direct pressure contact with the CO2 gas in said containerfor effecting said. movement of said refrigerant in said path under theinfluence of the pressure of said gas, a passageway for conducting saidgas from said container into said enlarged portion, heat responsivecontrolv means disposed in the region of said cooling unit including avalve in said conduit for opening and closing said conduit to flow ofsaid refrigerant upon predetermined changes of the temperature in saidregion. Y

5. In a refrigeration system, a support for holding a body of solid CO2thereon in a communication with the atmospherefor maintaining said body'at substantially atmospheric pressure during sublimation thereof, aclosed container for holding a substantially smaller amount of solid CO2than said body under pressure of the CO2 gas resulting from sublimationof said smaller amount, a liquid refrigerant, a. continuous conduit,including a cooling unit, enclosing said refrigerant for movementthereof in one direction in a closed path of travel, said supportcomprising a portion ofA one of the walls of said conduit whereby saidrefrigerant will be cooled upon passing said support, another portion ofsaid conduit being enlarged and alongside said container, meanscomprising a body of said refrigerant in said enlarged portion disposedin direct pressure contact with the CO2 gas in said container foreffecting said movement Aof said refrigerant in said path under theinfluence of the pressure of said gas, a passageway for conducting saidgas from said container into said enlarged portion, heat responsivecontrol means disposed in the region of said cooling unit including avalve in said conduit for opening and closing said conduit to flow ofsaid refrigerant upon predetermined changes of the temperature in saidregion, one of the walls of said enlarged portion being one of the wallsof said tank.

6. In a refrigeration system, a support for holding a body of solid C02thereon in communication with the atmosphere forV maintaining said bodyunder atmospheric pressure during sublimation-thereof, a closedcontainer for holding a smaller amount of solid CO2 than said body1inder pressure of the C0: gas resulting from sublimation of saidsmaller amount, an endless conduit, including a cooling unit, enclosingsaid refrigerant for movement thereof in one direction in a closed pathof travel, the upper side of said support on which said body is heldbeing corrugated with passageways in the ridges of such corrugationsextending longitudinally thereof and headers at opposite ends of saidpassageways, said passageways and said headers being part of saidconduit, a portion of said conduit adjacent said support and adjacentsaid container being enlarged, means comprising a body of saidrefrigerant in said enlarged portion disposed in direct pressure contactwith said CO2 gas for ef- 'fecting said movement of said refrigerant insaid path under the influence of the pressure of said gas.

7. In a refrigeration system in which there is a closed tank for solidCO2, a cooling unit, a control chamber, a support for holding arelatively large body of solid CO2 in communication with the atmosphere,and a passageway through said support one of the Walls of which is indirect heat transfer relation to said body, said cooling unit, controlchamber, and passageway being connected in series to form an endlessconduit for a liquid refrigerant, a CO2 gas pressure line communicatingbetween said tank and said chamber for providing gas pressure in saidchamber and on the liquid refrigerant therein for causing movement ofthe liquid refrigerant through said conduit under the influence of saidgas pressure, control means for said gas including a float in saidchamber and a guide element around said oat for guiding the latterduring vertical movement thereof, said float being supported on theliquid refrigerant in said chamber for` vertical movement upon risingand falling of the level of the liquid in said chamber, and meansactuated by said movement of said float for controlling the iiow of gasinto and out of said chamber.

8. In a refrigerating system of the character described, a verticallydisposed chamber having vertical side walls, a top, and a bottom, ahorizontal partition dividing said chamber into an upper compartment anda lower compartment, an inlet in said upper compartment `for admitting aliquid refrigerant into the same, a discharge outlet in said lowercompartment for discharge of a liquid refrigerant therefrom, a valvedpassageway communicating between said upper compartment and said lowercompartment for passing liquid from the upper one to the lower one, acylindrical wall depending from said top, a cylindrical float verticallyreciprocable within said wall upon rising and falling of the float asthe liquid level rises and falls, said wall having drain holes formedtherein spaced from the upper end thereof and being imperforate abovesaid holes for providing a gas trap between the uppermost of such drainholes and said top, a gas pressure line communicating with said lowercompartment and a vent for establishing communication between said uppercompartment and its lower one, valve means actuatable by said oat uponrising and upon falling to predetermined limits for opening and closingsaid vent.

9. In a refrigerating system of the character described, a verticallydisposed chamber having vertical side walls, a top, and a bottom, ahorizontal partition dividing said chamber into an upper compartment anda lower compartment, an inlet in said upper compartment for admitting aliquid refrigerant into the same, a discharge outlet in said lowercompartment for discharge of a liquid refrigerant therefrom, a'

providing a gas trap between the uppermost of such drainholes and saidtop, a gas pressure line communicating with said lower compartment and avent for establishing communication -between said upper compartment andthe lower one, valve means actuatable by said iioat upon rising and uponfalling to predetermined limits for opening and closing said vent, saidwall being provided with openings below its upper end for free passageof a liquid refrigerant therethrough.

10.i The method of` cooling and circulating a liquidrefrigerant in anendless enclosed path that includes the steps of effecting a heatexchange between said refrigerant and a -body of solid CO2 that is underatmospheric pressure at a point in said path and utilizing the CO2 gasfrom a confined body of solid CO2 for forcing said refrigerant aroundsaid path, and precooling said refrigerant by causing the latter to flowalongside said confined body of CO2 before reaching said point.

11. The method of cooling and circulating a liquid refrigerant in anendless enclosed path thai-I includes the steps of effecting a heatexchangev between said refrigerant and a body of solid CO2 that is underatmospheric pressure at a point in said path and utilizing the CO2 gasfrom a confined body of solid CO2 for forcing said refrigerant aroundsai-d path, and accelerating sublimation of the said confined body ofsolid CO2 by causing the liquid refrigerant to flow closely alongsidethereof immediately prior to said refrigerant reaching said point andafter said refrigerant has passed through the region to be refrigerated.

12. The method of refrigerating a storage space that 'comprisessimultaneously subliming a. relatively large amount of dry ice atatmospheric pressure and a relatively smal1 amount of dry ice in aconfined space under pressure of the gas so sublimed from said smallamount, circulating a liquid refrigerant in an enclosed path thatextends into said storage space and past said large body of dry ice indirect heat exchange relationship to the latter by means of the gasunder pressure from said confined space, and maintaining said gas at asubstantially uniform relatively low pressure.

REX L. BRUNSING.

REFERENCES CITED UNITED STATES PATENTS Name Date Brown June 23, 1942Number

